Torque-transmitting mechanisms, such as clutches and brakes, used in vehicle transmissions are designed to enable desired torque transfer while permitting controlled slip, if desired, upon engagement. Achieving the appropriate slip is dependent on many factors, such as whether the torque-transmitting mechanism is for low pressure or high pressure engagement, and the slip speed. Clutch durability, cooling flow, and required torque capacity must be considered.
In vehicles in which an engine is coupled with a transmission via a torque converter (i.e., a fluid coupling) to provide a ratio boost, a torque converter clutch is often provided to bypass the fluid coupling under certain operating conditions, typically leading to an increase in fuel economy or enhanced ride quality. The torque converter clutch may be a wet friction interface for establishing torque transfer under a slip condition (i.e., relative rotation of opposing surfaces forming the friction interface).